StingrayLust

I recently replaced my '71 points distributor with an HEI unit. In doing so, I needed to add a new 12V source. I was told that the IGN fuse box post is the correct location to attach to.

However, when I tried to start the car for the first time yesterday, it would not start. I took my voltmeter and checked for 12V right at the IGN fuse box post and couldn't get a constant 12V reading, it would just jump all over the place. So for the time being, I had to temporarily hook it up to the BAT fuse box post to get it started, which meant I had to pull wire to stop the engine.

The question is, I should be getting a constant 12V reading on the IGN post right?

Paul L

My answer would be no. The IGN terminal on my 1974 is occupied by the power window wiring (stock/factory) and I have added daytime running lights there. Both are ignition-switched. Key off, no power.

StingrayLust

I know the post is ignition switched, that's why my distributor should be tied to it, so when I turn the key off the car stops.

What my question was asking is that if I stick a voltmeter to the IGN post, it should read a fairly constant 12V when the key is on. When I have my key on my IGN fuse box post doesn't read a constant 12V, the digital readout jumps all over the place.

...Roger...

It should read constant,try pulling out the DIR SIG fuse right next to it ,clean the term and maybe replace the fuse and then retest.

StingrayLust

I had all of the fuses out when I went to put in the 20A fuse in next to the IGN switch. Here is a picture of the fuse box before I took out all of the fuses:



I'm not sure yet what that existing wire pink/black is for as I haven't traced it, but it's going into the exact slot I want to hook up my distributor to.

I'll try cleaning it next and see if it was just rusty and that caused the bad reading.

Paul L

Those are the power window wires with an AUX included on the side. I used the AUX for my DRLs. This pic shows the AUX on that line. The red wire is my add-on for the DRLs. It runs to a control module at the front of the car. The in-line fuse is installed but at this point I had not added the connecting terminal to the AUX.

ElCameeeno

I get a steady 14.1v at the IGN terminal.

Paul L

Sounds as if the car was running. I didn't measure but the AUX I have shown should be good for the HEI input.

ElCameeeno

Oops sorry, should have clarified that. 14.1 running, 11.7 or so with the engine off.

Paul L

Sounds like a healthy system!

...Roger...

How are your turn signals and back up lights acting,its same fuse ?

Have you considered powering your dist from the 12 pink coming off the ignition switch ? That's where GM gets the power for HEIs.

Paul L

True, Roger. But that does not explain what seems like a problem at the fuse box. I would hunt down that malfunction as well.

*Edit* - I remember years ago I lost a lot of electrical functions on my 1967. One of the bulk connectors on the firewall side of the fuse box had come loose and there was some corrosion. I cleaned things up and used di-electric grease to re-connect. A little Goop to hold things in place as well (yes, I am Bubba). All was well afterward. Just a thought.

StingrayLust

That was it, I had been assuming it was the fuse to the left of the IGN post when Roger was correct, the power comes from the DIR SIG fuse. As soon as I put the fuse in there, my IGN post showed the correct 12V.



That's the biggest noob error I've made in some time on this car.

dembo

Roger made a good point, when you look at a 75 diagram, the HEI is powered by the 12 pink going to the ignition switch. That's what I did using a Scotch lok, keeping the IGN terminal free for other goodies
Regards,
Nick

Paul L

I am pleased that you got that matter sorted out. Happy motoring!

...Roger...

Super

For future reference-generally fuses on the left are hot 24-7
................fuses on the right are Ignition switched
the tiny Inst LPS fuse at the bottom is hot "only" when the HL switch is pulled out.

...Roger...

That's exactly what I do. The Scotchlock makes a good connection,it can be reversed in the future if you want to go back to points.
Bubba ? No-way , GM used them also in most C3s.

The IGN spade is OK but it is fused and already carries a load from the Turn signals and Backup lights,a short in either one would shut down the engine.

Paul L

The IGN spade is OK but it is fused and already carries a load from the Turn signals and Backup lights,a short in either one would shut down the engine.

Interesting, and an excellent point. Is the new hot wire (pink) to the HEI fused?

...Roger...

No,it doesn't have a dedicated fuse. It would be fused by 1 of the fusible links at the starter or horn relay depending on the year of the car.
This is the same for factory HEI cars.

StingrayLust

I'm a bit confused. The IGN post must be fused by the DIR SIG fuse as I wasn't reading 12V on there until I put in the 20A DIR SIG fuse.

However Paul74 is correct, if I had a short in my lights that caused the fuse to blow my engine would shut down. I don't quite remember what gauge of wire I used from the fuse box to the distributor (it was either 12 or 14) and I didn't put in any additional fuses in there thinking that the fuse box would already have that covered.

The hot pink (black stripe) wire in my photo was already on the car when I bought it and I believe someone said it went to the power windows?